Children in the US are exposed to various neurotoxicants that can damage their developing brains. We have recently shown that the long-known negative impact of low SES on cognitive development is mediated by differences in brain structure. Specifically, the association between brain structure and SES is more pronounced in the poorest children, those who are often the most exposed to neurotoxic metals, such as lead (Pb). Here, we aim to better understand the impact of perinatal Pb exposure on brain, cognitive and behavioral development longitudinally using a novel tooth dentine assay. This novel measure allows quantification of prenatal and postnatal Pb exposure beginning with the 2nd trimester in utero and ultimately until the tooth is shed during later childhood; dentine develops over time, much like rings of a tree, trapping earlier exposures beneath the next ?ring? of dentine to form, allowing temporal measurements of Pb in consecutive rings of dentine. The effects of Pb exposure may be exacerbated in the context of low SES, but this important aspect of brain development in the environmental setting has received little research attention. In this proposal, we will leverage substantial existing funding by investigating Pb exposure among a subset of ~500 participants of the Adolescent Brain Cognitive Development (ABCD) study who have donated shed deciduous (baby) teeth. We will also leverage recent funding from the Children's Health Exposure Analysis Resource (CHEAR: Project #2017-1920; now HHEAR) to cover the costs of tooth analysis at three distinct developmental periods: the 2nd trimester and 3rd trimester of fetal development and the 1st year of life. Notably, the ABCD cohort of over 11,800 participants varies considerably on race and ethnicity, geographic location, family income, and parent education, and nearly 4,000 participants have donated teeth. This will allow a strategic selection of participants who are matched by Pb risk measures (based on publicly available risk maps of Pb exposure geocoded to each participant's home address) while controlling for SES and race factors that could be confounded by risk of Pb exposure. Pb risk may increase the likelihood of exposure, but it is clear that some at high risk could have low exposure whereas some at low risk may have high exposure. While our preliminary studies show that Pb risk status is associated with brain, cognition, and behavior as a function of SES in the ABCD cohort, only by measuring endogenous Pb levels within groups of individuals matched on SES by risk status can we determine how and where to focus future efforts to reduce remediable Pb risk factors and improve the health of children in the US. In this proposal, we will assess (1) associations between dentine Pb levels on structural brain development during childhood and determine if associations vary as a function of level of exposure at 3 developmental time points, (2) associations between dentine Pb levels and cognitive and behavioral development along with sex differences on these associations, and (3) the moderating or mediating effects of SES on brain-cognitive-behavioral development in the context of perinatal Pb exposure.